Coding device and position-determining device and position-determining method

ABSTRACT

In order to increase safety, a computer-implemented method is proposed for determining the position of a lift cabin in a lift shaft with the aid of a coding device, which comprises a code band as a marking, wherein the position is determined analytically by means of an algorithm on the basis of the code of the marking, wherein an extrapolated position is determined from the stored positions and the instant of the recording and, in turn, a coding pattern to be compared in relation to the recording is calculated by inverting the algorithm.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No.PCT/EP2014/002766 filed Oct. 14, 2014, which designated the UnitedStates, and claims the benefit under 35 USC §119(a)-(d) of EuropeanApplication No. 13004910.9 filed Oct. 14, 2013, the entireties of whichare incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a coding device for marking positionsin a lift shaft and for determining the position of lift cabins in thelift shaft, to a computer-implemented method for determining theposition of a lift cabin in a lift shaft with the aid of a codingdevice, and to a position-determining device.

BACKGROUND OF THE INVENTION

The prior art, for example EP 0 722 903 B1, has disclosed a method inwhich a lift cabin is displaced in the lift shaft along a code band,wherein the lift cabin comprises a detector and, when the detector comesacross an image pattern applied to the code band, it compares the latterwith a reference pattern and derives information for the controller fromthe identified pattern.

SUMMARY OF THE INVENTION

An object of the present invention is to be able to provide a code band,a position-determining method and a position-determining device whichenable an increased level of safety in operating the lift.

The present invention firstly makes available a code band in the case ofwhich discrete positions are admittedly marked, but can, however, beprovided in a density such that the lift cabin can read out its positionpractically permanently. The control unit for controlling the lifttravel, that is to say its closed-loop and/or open-loop control, canthus be provided permanently with the information relating to thecurrent position of the travel cabin, and there are practically nodistances along which the travel cabin is driven “blind”, that is to saywithout concrete position information, and cannot react until it meets amarking which is intended, for example, to cause the cabin to brake.This measure enables a high degree of safety in operating the lift. Inaddition, the present invention offers reliable and safe operation ofthe lift cabin, because the type of coding device and ofcomputer-implemented method for determining the position enablesinspection options, redundancies and plausibility checks by means ofwhich high safety standards can be achieved. In particular, it is alsopossible to read out positions even when the code band is, for example,soiled and it is therefore no longer possible to read out all theinformation held there.

A further advantage of the present invention consists in that preciselyin connection with the use of a coding device according to an exemplaryembodiment of the present invention having bearing devices, there is, inaddition, the possibility of being able to take account of the subsidingof a newly constructed building when evaluating and determining theposition of the lift cabin, even of being able to correct thedetermination of position. Newly erected buildings mostly have theproperty that they “subside” with time, that is to say instances ofcompression can occur in the building in the course of time because ofthe high weight loads. This effect can occur precisely with highbuildings, which mostly have a lift. It is a particularly problematicfeature of this effect in the construction of buildings that not allparts of the building respond uniformly thereto. In particular, as arule, the lift structure in which the travel cabin is mounted to bedriven is not affected thereby, or is at least only partially affectedthereby. In such a case, the partial compression of the building wallmeans that the travel cabins are also displaced with respect to theframe of the lift shaft. Such a correction, which is likewise enabled bythe invention, can compensate this phenomenon of the subsidence of abuilding. In particular, it is possible thereby to increase the safetyand reliability in operation of the lift.

The inventive coding device serves for marking positions in a liftshaft, and for determining the position of lift cabins in the liftshaft. It comprises a code band which is, for example, suspended andfastened in the lift shaft on the ceiling of the building. The code bandis mounted to move in the lift shaft via a bearing device. When, forexample, the building subsides and is partially compressed inwardly, thecode band can appropriately move downward together with the ceiling ofthe building and yet continue to hang freely, because it is mounted tomove inside the bearing devices and not held fast. Consequently, thefreely hanging code band must also not bend or be compressed duringsubsidence of the coding. The markings on the code band are providedalong its length, for example equidistantly. The markings can bedesigned as a barcode, but particularly preferably as 2D code(two-dimensional code). Firstly, such a 2D code visually delivers aparticularly advantageous, simplified detection, but also a high densityof coding options.

In principle, a barcode can be arranged in a row, but a 2D code(two-dimensional code) can likewise be provided accordingly. A 2D codeis normally designed as a matrix, it being possible for the individualmatrix elements to form bright or dark, that is to say the values 1 or0. One or more rows can mark a discrete position as such. It isparticularly advantageous for this type of markings that they can notonly be easily detected and read out, but also can be decoded by meansof an algorithm and be processed mathematically. The advantage islikewise achieved thereby it is possible to avoid complicatedcomparisons of images with reference patterns which, on the one hand,can be more prone to error but, on the other hand, also requirecomputers of high graphic computing power and, moreover, necessitatememories with high capacity for storing the reference patterns. Inaccordance with the present invention, the mathematical algorithm can beevaluated with the aid of a computer, and, if appropriate, even by meansof a simple microcontroller or microprocessor. This advantage in timealso enables the markings to be evaluated very quickly so that even inthe case of high marking density, the travel cabin can be permanentlyinformed of its position in the lift shaft during its trip.

The computer-implemented method according to the present inventioncomprises the following method steps: image processing, an analysismethod with a position pattern analysis, an extrapolation method and acomparison method.

The image processing provides the following steps:

-   -   A section of a code band and/or of the bearing device is        recorded with an optical detection device as a pixel image        consisting of pixels, the instant of the recording is measured        and assigned to the pixel image, wherein the recorded section is        selected to be so large that it comprises at least one more row        than the position marker.    -   The pixel image is processed, in particular, assigned to a        detection grid, wherein pixels of the pixel image preferably are        combined with the aid of their color and/or position in order to        be able to read out the barcode and/or 2D code of the marking.

In a first step, the analysis method provides a position patternanalysis, in which

-   -   the position marker is identified on the basis of the part of        the marking for characterizing the position marker,    -   a position code is identified in the detection grid, in        particular as a barcode and/or 2D code, on the basis of the        position marker,    -   the position code is converted to a binary code,    -   the binary code is decoded by means of an algorithm and        converted into a position indication and/or into information as        to whether a bearing device has been detected,    -   the determined position indication is stored together with the        assignable instant of the recording and/or together with        indications about the movement of the lift cabin, such as e.g.        velocity and/or acceleration, wherein the first partial method        is repeatable at certain, preferably equal, time intervals of a        travel of the lift cabin in order to be able to continuously        obtain or generate position information during the travel.

Together, the image processing and the position pattern analysis form afirst partial method.

An extrapolation method is carried out as a second partial method, inwhich:

-   -   a check is carried out as to whether at least two stored        position indications and the instant of recording thereof are        stored,    -   an extrapolated position of the lift cabin is calculated (E)        from the at least two position indications, the instants of the        recording thereof and the indications about the movement of the        lift cabin.

A third partial method is a comparison method, in which:

-   -   a barcode and/or 2D code and/or a position marker is calculated        from the extrapolated position indication on the basis of the        inverse of the algorithm and compared with the position marker        determined from the first partial method,    -   wherein, in particular, the extrapolated position indication is        output as position indication if the extrapolated position        marker and the recorded position marker differ by at most a        predetermined number of bars of the barcode and/or matrix        elements of the 2D code.

In a preferred embodiment of the present invention, the comparisonmethod is complemented by an acceleration correction, i.e., there is adetermination that the extrapolated position is affected by errors. As apossible error source, the assumption is made, for example, that thevelocity of the lift cabin was not known completely exactly, that themeasurement of the time is affected by errors or that other statisticalor systematic errors may occur. However, such an error is generally notrelevant to the position of the lift cabin if the deviation from theactual position is only small. In order to undertake the accelerationcorrection, a small error can be assumed initially and, if the positioncomparison should fail, an ever larger error can be assumed.Consequently, it is therefore possible to take into account increasinglyspaced apart marking rows. In this manner, the method in accordance withthis exemplary embodiment of the present invention can take into accounterrors occurring in reality for as long as these are not so grave thatthey would put at risk the correct operation of the lift. If theseerrors were not taken into account, non-determinable positions couldarise more frequently, which would make operation more difficult orrender the evaluation more complicated.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention are illustrated in thedrawings and explained in more detail below with an indication offurther details and advantages.

FIG. 1 shows the reading out of the coding device in accordance with thepresent invention by an optical detector;

FIG. 2 shows a schematic illustration of a camera recording;

FIG. 3 shows a pair of pixel strips;

FIG. 4 shows an extended image pattern;

FIG. 5 shows an image pattern;

FIG. 6 shows a position pattern;

FIG. 7 shows an overall scheme of the computer-implemented method inaccordance with the present invention;

FIG. 8 shows a schematic illustration of the image processing;

FIG. 9 shows a schematic illustration of the analysis method;

FIG. 10 shows a schematic illustration of the comparison method; and

FIG. 11 shows a schematic illustration of the correlation method.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a detection device 1 which reads out a code band 2 in alift shaft. Provided for this purpose on the lateral edges of the codeband are position strips 3 which laterally delimit the 2D code 4. Thecoding device comprises the code band 2 and a clip 7. The code band 2 ismounted to move with such clips 7 as a bearing device such that it canbe displaced in a longitudinal direction when, for example, the buildingsubsides with time. The clip 7 comprises a bridge 8 which overlaps thecode 4 and/or the position strips 3. The detection device 1 basicallycomprises two cameras whose detection beams 9, 10 for recording adetection image are likewise illustrated in FIG. 1.

FIG. 2 shows the recorded image section 1 of the camera, which wasrecorded by the code band 2. The recording 1 overlaps the lateral edgeof the code band 2. Position strips 3 are provided at the outer edges ofthe code band in a longitudinal direction of the code band 3. The stripsare completely black in design and are therefore easily detected by thedetection device and the evaluation method. These position strips 3likewise provide screening, such that the evaluation method is able todetect the region in which the 2D code 4 is to be found. The 2D code iscomposed of a matrix 4 which has individual matrix elements 5, 6. Thematrix element 5 is a bright one, while the matrix element 6 is a darkone. However, in general, the matrix elements 5, 6 do not correspond ineach case to a single pixel of the camera recording. Consequently, it isnecessary when processing images to assign recorded pixels to oneanother in accordance with their position and their brightness andcombine them to form a matrix element. In the combined image, in turn, apixel then represents a matrix element. Specified in FIGS. 3 to 6 aresections processed by image processing B and in the case of which camerapixels have been processed to form matrix elements.

An overall illustration of a computer-implemented method for determiningthe position is illustrated in FIG. 7.

Camera Recording K

The detection device 1 enables optical detection of the markings 3, 4provided on the code band 2. The camera (optionally including aplurality of cameras) generally operates in the infrared region (IRlight, wavelength approximately greater than 780 nanometers to 1millimeter), so that in particular, it is also possible to avoidinterfering influences. If the cabin is traveling in the lift shaft inwhich the code band 2 is also suspended, the cabin will move along thecode band, the camera being aligned such that it can correspondinglydetect the code band. During the trip, the camera repeatedly takesrecordings K of sections of the code band (in particular, in equal timeintervals), compare FIG. 2. Such a pixel recording can typicallycomprise 100×24 pixels and be recorded as a grayscale image (for example12-bit image). At the same time, in the present case a clock or a timeris provided which assigns a timestamp depending on the camera recording,that is to say a time information item, when the recording is finished.This timestamp later enables evaluation of the images when furtherinformation is known, that is to say, for example, individual positionsat specific instants, speed of the lift cabin or acceleration of thelift cabin.

Extrapolation Method E

The aim of the overall method from FIG. 7 is to determine the positionof the lift cabin, specifically at different instants, making itpossible, as already described, for the individual positions also to begiven by timestamps. In a further method step, a check is made after thecamera recording K as to whether there have already been determined in amemory two positions in relation to which two timestamps are alsopresent. If this is the case, the position can be determined at afurther, third instant (extrapolation). If the cabin has not carried outany uniform movement, the extrapolation can be performed, ifappropriate, by taking account of the speed, known from the open-loop orclosed-loop control of the cabin, of the lift cabin, or the accelerationof the lift cabin. Given uniform movement of the lift cabin, the speedthereof can be determined from two positions and their timestamps, thatis to say the time information item, once these positions have beenreached. If there is no change in this speed, the position cancorrespondingly be obtained therefrom at a further, third, instant. Ifthe lift cabin accelerates in this time, or if the lift cabin is brakedin this time, this must be appropriately taken into account. These data,relating to the acceleration and, if appropriate, also to the speed, canbe retrieved and read out in embodiments of the invention by the controldevice of the travel cabin (open-loop or closed-loop control). If fewerthan two positions are stored after carrying out the camera recording,the next method step is adopted without extrapolation taking place.

The precondition for carrying out the extrapolation method E is that atleast two positions and three timestamps are stored. The two positionsserve for being able to determine a path difference between the twopositions. If two further timestamps are available, each of which isrespectively assigned to one of the two positions, it is also possibleto determine the time difference required to reach the other positionproceeding from one of the two positions. The third timestamp isrequired in order, finally, to be able to determine the further positionto be extrapolated. Thus, before actually carrying out the extrapolationmethod, a check needs to be made as to whether this precondition that atotal of two positions and three timestamps are stored is satisfied.

Image Processing B (FIG. 8)

The next method step consists of image processing. A grayscale image hasbeen recorded in the camera recording. It is also conceivable, inprinciple, to immediately record a black and white image, the more so asthe code 4 imprinted on the code band 2 is designed as a barcode or 2Dcode, and therefore basically consists of only two colors orbrightnesses. However, it must be taken into account that it is notalways possible to exactly detect the same brightness values of asurface by influences from ambient light, deposits on the code band,slight differences in distance or in detection angle. Black surfacesthen, as the case may be, appear more or less gray. In order to be ableto take account of this effect, it is advantageous to record a grayscaleimage and to decide with the aid of the color, here with the aid of athreshold value of a grayscale or brightness, whether the detectedsurface or the detected pixel is to be assigned to a dark or a brightregion with reference to a barcode or a 2D code. If appropriate, thisthreshold value can also be set as variable, thus likewise in principleenabling readjustment. For one thing, the recorded images can thereby beconverted in principle into a 1-bit image. Secondly, it is to be bornein mind that a type of image detection or assignment to a screen is alsoperformed in the image processing.

In this way, it is possible to separate (in the present case) two pixelstrips which comprise 2×24 pixels and whose longitudinal extent runsalong the columns S (compare FIG. 3).

Furthermore, an image pattern and an extended image pattern aregenerated (FIGS. 4 and 5). The extended image pattern is illustrated inFIG. 4 and consists of 8×7 matrix elements in a black and white image,that is to say 1-bit representation. In these generated patterns, thematrix elements are represented in each case as a pixel in a fashioncombined and reduced in size. The extended image pattern in accordancewith FIG. 4 therefore has more rows Z than the image pattern inaccordance with FIG. 5 because, as explained later, the bridge 8 of abearing device 7 or of a clip can comprise three rows. In addition, eachposition marker, which has the complete information relating to a singleposition, comprises three rows in the present exemplary embodiment. Ifappropriate, additional rows may be required for individual evaluationmethods.

The simple image pattern is illustrated in FIG. 5 and has only fiverows, likewise illustrated in black and white, that is to say one-bitrepresentation. The entire 2D matrix pattern comprises ten columns. Theouter right and the outer left column 11 serve the purpose of separatingposition markers, that is to say coherent regions of the matrix whichcompletely code a separate position, that is to say of marking where theposition starts and stops. This is required so that in the event ofrandom recording of an image it is clear where the position is markedand that parts of two different position markers are not being evaluatedtogether, something which could result in an incorrect positionindication. The rows of the matrix are arranged without spacing from oneanother in the present exemplary embodiment, thus enabling a higherdensity of the markings.

FIG. 6 shows a position pattern with only three rows, that is to say aposition marker with the complete coding of a specific position.

As already described above, the code band is mounted to move in bearingdevices for the movable bearing of the code band which are fastened onthe wall of the lift shaft. These so-called clips 7 overlap the codeband 2 toward the lift cabin (with the bridge 8), that is to say towardthe side on which the marking of the code band is located. The cliptherefore partially covers the code band in principle. At this point,the position would thus not be “detectable” in principle during a camerarecording. Consequently, it is advantageous to detect the clip as such.The inventive coding device is particularly advantageous to the effectthat the clip need not be detected as an image however, but that it cansurprisingly be evaluated together with the code band. To this end, thebridge 8 of the clip, which projects beyond the code band and isdetected, has a coding pattern which corresponds to that of the codeband, that is to say a barcode or a 2D code.

It is particularly advantageous to configure the code mapped on the clipin as simple a way as possible, in particular in a color of the barcodeor 2D code coding, that is to say black or white or bright or dark.Firstly, the production of the clip is thereby simplified. Secondly, theclip can thereby be easily detected, something which is particularlyadvantageous because the construction phenomenon of the subsidence ofbuildings can entail the clip moving relative to the code band when thebuilding subsides over time. The clip then changes its position relativeto the code band upon subsidence of the building. It is thereforeadvantageous to provide only one of the markings with an absoluteposition indication, specifically either the code band or the clip, sothat a comparison can be appropriately carried out. The clip cantherefore be found by a mathematical analysis or the carrying out of analgorithm. This clip identification is performed in the image processingvia the extended image pattern. A pixel row analysis is performed inwhich the cross sum over the detected matrix elements is formed. In thepresent case, the clip is designed as black, and so a check is made asto whether the cross sum over the matrix elements yields zero. If thisis the case, it can only be a clip which is concerned, since the codingis selected such that other rows cannot have the cross sum 0.

Since it is also known how many rows the clip is using, for example,three rows, its position can also be determined. If, for example, onlyone row is completely black at the upper image edge, the clip iscorrespondingly located in the upper region of the camera recording. Ifall rows of the clip can be detected, it is located at a correspondingpoint in the camera recording K. An immediately adjacent position cantherefore be assigned by a completely mapped position marker. If, in thecase of an embodiment, there is no longer enough space to detect acomplete position marker, it is necessary, if appropriate, to derive theposition of the clip via extrapolation, or to assign the clip anappropriate position. When detecting a clip, it is not always necessaryto assign its exact position; it is always sufficient to assign theclips a position in the same way, for example, with a constant offset,since it is generally necessary to establish only relative distancesbetween the clips, in order to establish, for example, how strongly abuilding has subsided. By way of example, the lower edge of the clip isdetermined with regard to its position in the present case.

Clip Position C

In a further method step, it is established whether an extrapolatedposition has already been generated at all. If it is the case, it isfurther decided whether it was possible to identify a clip and whether aclip pixel position has been obtained. If this is likewise to beanswered in the affirmative, the next partial method is that ofdetermining C the clip position (FIG. 7). With the aid of the priorinformation relating to the clip position, the extrapolation method E isused to extrapolate a position of the clip. If this extrapolatedposition corresponds at least approximately to the clip position, theextrapolated position is output as position and, if appropriate, so alsois an information item as to whether a clip was present or not. Thisinformation item can be designed as a 1-bit information item (clip bit).Finally, the clip is assigned its corresponding position (method stepCP) and output. The clip position itself can likewise be stored and usedlater for a correction when the building has subsided.

If, by way of example, the lift has only just started and for thisreason two positions have not yet been stored, the so-called analysismethod A is firstly carried out.

If a position can be obtained from the detected position pattern and atleast one clip bar is detected in part, the exact position of the clipbar must be extrapolated. Then, the position of the clip bar isgenerally slightly displaced in relation to the detected position. Ifthe clip bar completely covers the position pattern, it may be possibleto extrapolate the new position from the positions stored in the past.By way of example, if the clip bar completely fills the positionpattern, it is not possible from the clip bar alone to deduce theposition thereof in the present exemplary embodiment, and so theposition must be extrapolated from the previously stored data.

Analysis Method A (FIG. 9)

In the analysis method, the image pattern determined by the camera isfirstly used to undertake a checksum test, that is to say a check ismade as to whether the detected matrix elements yield a specialchecksum. In addition, the position marker (FIG. 6) is determined withthe aid of the lateral edges 11, and the position of the recorded imageis determined with the aid of the prescribed algorithm. The calculatedposition serves in the present case to infer with the aid of the inversemethod of the algorithm which further rows border on the positionmarker. These have likewise also been recorded by the camera. Acomparison is then undertaken as to whether these calculated patternsalso correspond to that of the regions bordering on the positionmarkers. These regions, which border on the position marker, thereforedo not need to be used in addition to calculating a position. Dependingon how many of the upper and lower edge regions are indicated inside thecamera recording K, this is, as the case may be, not even possiblestraight away. If these generated codings correspond to the actuallyrecorded codings, it may be concluded with very high probability thatthe position indication is actually correct. This position can then beoutput (position output OUT in FIG. 7), it likewise being possible,optionally, to perform an additional assignment of the clip positionwhen a clip has been detected. If an extrapolated position has beengenerated, but no clip recorded, the comparison method is carried out.

As already explained above, the position pattern, which has three rowsin accordance with FIG. 6, contains all of the position information.However, the analysis method uses the image pattern which comprises tworows more than the position pattern. It is therefore possible to deducethe two adjacent rows from the position pattern, to which an inversemethod of the algorithm for determining the position can be applied.Thus, a corresponding image pattern to be expected is generated andcompared with the actual image pattern (cf. FIG. 5). In the case of acorrespondence, the established position is the actual position of thelift cabin with a high probability. As can be seen in FIG. 4, a clip barcomprises a width of three rows which, in terms of size, corresponds toa position pattern. Thus, if the clip bar appears in an image pattern,what may occur, for example, is that the latter, without the upper andlower row, forms precisely the filtered out position pattern. The clipcan accordingly be identified as such by virtue of the cross sum beingformed over the grayscale values in the pixel image and being comparedto a grayscale value threshold value.

The clip bar is black in the exemplary embodiment. Since the value zerois assigned to the color black, this yields a cross sum of zero in theideal case as only black pixels were detected. However, what may happenin reality is that, for example, a dark grayscale value is detectedinstead of an ideal black value, and so it is generally advantageous toset the threshold value not to zero but to a specific threshold value asa function of the grayscale values to be expected during the detection.If the clip is only partly in the position pattern obtained from theimage pattern, a deduction about the actual position is neverthelesspossible from the identified rows, taking into account the clipposition. In the present exemplary embodiment, the code is selected insuch a way that each row is, in fact, completely individual and does notoccur a second time on the code band. If a clip bar is detected and itonly makes up part of the position pattern, the uppermost or lowermostrow of the image pattern must likewise automatically form part of theclip bar in the present example. This can also be taken into account inthe full pattern test of the analysis method.

The high level of safety is ensured because it is not only thedetection, which may, as a matter of principle, be afflicted by errors(be it by dirtying, additional reflection or other erroneousdetections), that is taken into account, but also because part of thedetection previously not taken into account is resorted to on the basisof inverting the algorithm and deductions in respect thereof are made.

Comparison Method V (FIG. 10)

Apart from the image pattern, the extrapolated position is required forthe comparison method (FIG. 7). The image pattern to be expected isdetermined from the extrapolated position alone and compared with thatactually recorded. If the comparison is exactly correct, it can bededuced therefrom that the correct position has actually been found, andthe extrapolated position is output as the position indication OUT.However, it can happen that although the extrapolated position and theactual position correspond, the recorded image can nevertheless beincorrectly processed because, for example, the code band is soiled atsome points, or because other disturbing influences have played a role.If the code is selected such that only one or only a few matrix elementsdo not change from one row to the next, it is possible to tolerate aslight deviation in the case of a few matrix elements, and neverthelessto assume that the extrapolated position is actually present andcorresponds to that recorded. In the present case, this can, forexample, be assumed whenever fewer than four matrix elements deviate. Itis particularly advantageous to this end to select the coding forreasons of safety such that the coding can deviate strongly from one rowZ to the next. For example, the algorithm can provide a code in the casethe matrix elements are interchanged in a prescribed way as a functionof the position of the row, something which can easily be implementedwhen the algorithm is known. However, if the deviation is too large, amethod can be carried out with an acceleration correction. Particularlywhen the lift cabin is accelerated or decelerated while it is travelinguncertainties occur with regard to the extrapolation, since thesechanges in speed in time would need to be detected accurately, and thespeed would have to be detected by integrating the acceleration overtime. For technical reasons, this cannot generally be undertaken soaccurately that deviations would be inconceivable, especially as themarkings, for example, are provided with a spacing of half a millimeter.

An acceleration correction is optionally carried out with a type ofposition variation, this would firstly likewise require the extrapolatedposition indication. The image pattern is now generated on the basis ofthe extrapolated position indication, which has been calculated, as arethe further rows, which directly border on the position marker of thegenerated image pattern. The recorded pattern is thus compared withimage patterns which are to be found one, two or three lines above theimage pattern, since it corresponds to the extrapolated positionindication. If the recorded image pattern exists in this region, it canbe assumed that the position determination has deviated within atolerable limit, and that the extrapolated position is the outputposition. If this comparison also delivers no result, a correlationmethod is carried out. The pair of pixel strips known from FIG. 3 isused to this end.

Correlation Method KV (FIG. 11)

The first requirement is the generated pair of pixel strips (see FIG.3), specifically in each case a current pattern and a pattern previouslyrecorded during the trip. These pixel strips, which have been recordedat different times, are, to a certain extent, laid one over another anddisplaced until agreement is reached. In this case, the determination isdone in accordance with the offset. In addition, a plausibility checkcan be carried out with the aid of the extrapolated position. Since thedetection device comprises two cameras overall, a second comparison canalso be carried out during the correlation method KV with the aid of asecond camera (second camera image K′ in FIG. 7), and examined forconsistency. When this correlation method KV also leads to no consistentresult, a further extrapolation method E which proceeds analogously tothat described above can be carried out once again. When this also leadsto no result, it is necessary to carry out a new camera recording, sinceno position can be determined. If appropriate, a case of emergency isoutput when no position at all can be determined.

It is also conceivable in principle, in particular, to combine theanalysis method, the comparison method or the correlation method withone another in another way, for example in a different sequence.

LIST OF REFERENCE SYMBOLS

-   1 Detection device-   2 Code band-   3 Position strip-   4 2D code-   5 Matrix element-   6 Matrix element-   7 Clip-   8 Bridge-   9 Detection lighting-   10 Detection lighting-   11 Marking columns-   A Analysis method-   B Image processing-   C Determination of the clip position-   CP Clip position assignment-   E Extrapolation method-   K Camera recording-   K′ Second camera recording-   KV Correlation method-   V Comparison method-   OUT Position output

1. A coding device for marking positions in a lift shaft and fordetermining the position of lift cabins in the lift shaft, comprising acode band, the code band has at least three markings arranged along thelength of the code band in order to mark discrete positions in eachcase, the markings are embodied as a barcode and/or 2D code, themarkings are arranged in such a way that they form rows and, inparticular, there are at least as many rows as there are discretepositions to be marked, the markings are embodied in such a way thatthey comprise a position marker for each discrete position to be marked,the markings are decodable by means of an algorithm, wherein, inparticular, there exists a mathematical function which uniquely assignsthe corresponding position to each marking of a position, at least onebearing device is provided for bearing the code band in the lift shaftsuch that it can be moved, in particular be moved longitudinally, saidbearing device being embodied to overlap the code band at least partly,preferably completely, and being embodied in such a way that it carriesa marking, in particular a barcode and/or a 2D code, arranged in such away that it covers at least part of the marking of the code band in areadable manner when overlapping the code band.
 2. The coding deviceaccording to claim 1, wherein the markings are arranged in such a waythat they form at least two columns.
 3. The coding device according toclaim 1, wherein the position markers are embodied in such a way thatthe discrete position is coded in at least two rows.
 4. The codingdevice according to claim 1, wherein a part of the marking is embodiedto characterize the position markers.
 5. The coding device according toclaim 1, wherein the markings are applied without a spacing and/orequidistantly on the code band.
 6. The coding device according to claim1, wherein the bearing device comprises a bridge in order to overlap thecode band on the side on which the markings are applied and/or which isto face a detection device.
 7. The coding device according to claim 1,wherein the markings of the at least one bearing device are applied onthe bridge and, in particular, only have a single-color embodiment,preferably in precisely one of the two colors of the barcode and/or 2Dcode, preferably corresponding to the darker code color, particularlypreferably being black.
 8. A computer-implemented method for determiningthe position of a lift cabin in a lift shaft on the basis of a codingdevice according to claim 1, wherein the following steps of a firstpartial method are carried out, by virtue of: a section of a code bandand/or of the bearing device being recorded with an optical detectiondevice as a pixel image consisting of pixels and the instant of therecording being measured and assigned to the pixel image, wherein therecorded section is selected to be so large that it comprises at leastone more row than the position marker, the pixel image being processed,in particular being assigned to a detection grid, pixels of the pixelimage preferably being combined with the aid of their color and/orposition in order to be able to read out the barcode and/or 2D code ofthe marking, the position marker being identified on the basis of thepart of the marking for characterizing the position marker, a positioncode being identified in the detection grid, in particular as a barcodeand/or 2D code, on the basis of the position marker, the position codebeing converted to a binary code, the binary code being decoded by meansof an algorithm and being converted into a position indication and/orinto information as to whether a bearing device has been detected, thedetermined position indication being stored together with the assignableinstant of the recording and/or together with indications about themovement of the lift cabin, such as e.g. velocity and/or acceleration,wherein the first partial method is repeatable at certain, preferablyequal, time intervals of a travel of the lift cabin, and wherein asecond partial method is carried out, in which: a check is carried outas to whether at least two stored position indications and the instantof recording thereof are stored, an extrapolated position of the liftcabin is calculated from the at least two position indications, theinstants of the recording thereof and the indications about the movementof the lift cabin, and wherein a third partial method is carried out, inwhich: a barcode and or 2D code and/or a position marker is calculatedfrom the extrapolated position indication on the basis of the inverse ofthe algorithm and compared with the position marker determined from thefirst partial method, wherein, in particular, the extrapolated positionindication is output as position indication if the extrapolated positionmarker and the recorded position marker differ by at most apredetermined number of bars of the barcode and/or matrix elements ofthe 2D code.
 9. The computer-implemented method according to claim 8,wherein a sequence of at least two position markers spaced apart fromthe extrapolated position marker is calculated and a comparison iscarried out between this calculated position marker and the detectedposition marker, wherein, in particular, the position corresponding tothe position for which the comparison yields complete correspondence orcorrespondence within a predetermined criterion is output as positionspecification.
 10. The, computer-implemented method according to claim8, wherein a sequence of at least two position markers spaced apart fromthe extrapolated position marker is calculated, wherein, to this end,use is made of position markers subsequently increasing in distancetherefrom.
 11. The computer-implemented method according to claim 8,wherein the optical detection of the section is carried out as agrayscale recording.
 12. The computer-implemented method according toclaim 8, wherein the grayscale recording is converted into a black andwhite image and/or a 1-bit image on the basis of a grayscale thresholdvalue.
 13. The computer-implemented method according to claim 8, whereinthe optical detections are carried out repeatedly during operation atequal time intervals.
 14. A position-determining device for determiningthe position of a lift cabin in a lift shaft, comprising: a detectiondevice for optically reading out the markings of the code band and acomputer for carrying out a computer-implemented method according toclaim 8.